Audi S4 C4 UrS4 2.2 20V Turbo

Audi S4 C4 UrS4 2.2 20V Turbo

The Audi S4 (C4), affectionately known as the 'UrS4' (Original S4) among enthusiasts, was Audi's first use of the S4 designation and one of the most significant performance sedans of the early 1990s. Built on the C4 100/A6 platform, it married the legendary 2.2-liter turbocharged five-cylinder engine — the direct descendant of the powerplant that had powered the Ur-Quattro to rally glory — with quattro permanent all-wheel drive and a refined chassis, creating a super sedan that was as capable in a blizzard as it was on an autobahn.

The AAN five-cylinder engine was a remarkable piece of engineering. Its 20-valve cylinder head (four valves per cylinder) breathed freely, while a single Garrett turbocharger provided boost pressure that elevated output to 230 horsepower and 350 Nm of torque. The five-cylinder configuration gave the engine a distinctive character — a throbbing, asymmetric exhaust note quite unlike any four or six-cylinder — that became an Audi signature and remains beloved by enthusiasts today. The engine's response was immediate and progressive, building boost smoothly rather than hitting the driver with a sudden surge.

The quattro system used a Torsen center differential that continuously distributed torque between the front and rear axles based on traction conditions. Under normal driving, the split was nominally 50:50, but the Torsen could send up to 75% of torque to either axle when conditions demanded. This provided extraordinary traction in all weather conditions — the UrS4 was legendary for its wet-weather and winter performance, maintaining composure and confidence when rear-wheel-drive competitors were struggling.

The six-speed manual gearbox — unusual for a sedan of this era — provided a wide spread of ratios that kept the engine in its most productive power band whether accelerating from rest or cruising at high speed. The shift action was precise if not quite as mechanical as a BMW's, and the gearbox proved robust even under the considerable torque loads of modified engines (the AAN is famously receptive to tuning, with aftermarket upgrades capable of doubling the stock output).

The UrS4's demeanor was that of a dignified, understated super sedan. The exterior was distinguished from the standard 100/A6 by only subtle cues: slightly lower suspension, unique alloy wheels, discreet S4 badges, and quad exhaust tips. The interior offered heated leather seats, walnut trim, and a comprehensive equipment level that befitted its price point. This subtlety was part of the car's appeal — it was a genuine sleeper, capable of humbling flashier competitors while appearing to be nothing more than an executive sedan.

The UrS4's importance extends beyond its own specifications. It established the S-model hierarchy at Audi and demonstrated that the quattro system could enhance a luxury sedan's performance rather than merely providing bad-weather traction. Every subsequent Audi S and RS model owes something to the template established by the UrS4, and the five-cylinder turbo engine it championed has been revived in modern Audi RS3 and TTRS models, proving that its character remains irresistible.